package com.ssq.mobilehelper.aes;

import android.annotation.SuppressLint;
import java.security.SecureRandom;
 
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;


/***
 *
 * AES 加密工具类
 */
public class AESUtils {
 //加密
    public static String encrypt(String seed, String cleartext)
            throws Exception {
 
        byte[] rawKey = getRawKey(seed.getBytes());
 
        byte[] result = encrypt(rawKey, cleartext.getBytes());
 
        return toHex(result);
 
    }
 //解密
    public static String decrypt(String seed, String encrypted)
            throws Exception {
 
        byte[] rawKey = getRawKey(seed.getBytes());
 
        byte[] enc = toByte(encrypted);
 
        byte[] result = decrypt(rawKey, enc);
 
        return new String(result);
 
    }
 
    @SuppressLint("TrulyRandom")
    private static byte[] getRawKey(byte[] seed) throws Exception {
 
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
 
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
 
        sr.setSeed(seed);
 
        kgen.init(128, sr); // 192 and 256 bits may not be available
 
        SecretKey skey = kgen.generateKey();
 
        byte[] raw = skey.getEncoded();
 
        return raw;
 
    }
 
    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
 
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
 
        Cipher cipher = Cipher.getInstance("AES");
 
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(
                new byte[cipher.getBlockSize()]));
 
        byte[] encrypted = cipher.doFinal(clear);
 
        return encrypted;
 
    }
 
    private static byte[] decrypt(byte[] raw, byte[] encrypted)
            throws Exception {
 
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
 
        Cipher cipher = Cipher.getInstance("AES");
 
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(
                new byte[cipher.getBlockSize()]));
 
        byte[] decrypted = cipher.doFinal(encrypted);
 
        return decrypted;
 
    }
 
    private static byte[] toByte(String hexString) {
 
        int len = hexString.length() / 2;
 
        byte[] result = new byte[len];
 
        for (int i = 0; i < len; i++)
 
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
                    16).byteValue();
 
        return result;
 
    }
 
    private static String toHex(byte[] buf) {
 
        if (buf == null)
 
            return "";
 
        StringBuffer result = new StringBuffer(2 * buf.length);
 
        for (int i = 0; i < buf.length; i++) {
 
            appendHex(result, buf[i]);
 
        }
 
        return result.toString();
 
    }
 
    private final static String HEX = "0123456789ABCDEF";
 
    private static void appendHex(StringBuffer sb, byte b) {
 
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
 
    }
 
}